Electrical switching unit



March 31, 1959 J. v. s. DAHLGREN E1-Al. 2,880,292

ELECTRICAL SWITCHING UNIT Filed April 19, 1957 FIG. 4 y

l I' H Hl II Ila lll |n INVENTORS JOHN V. S. DAHLG REN JOHN J. ROTHWELL United States Patentifv y ;z,sso,z9z ELECTRICAL swrrcHrNG UNrr .l'ohn V. S. Dahlgren, Fair Haven, NJ., and John J. Rothwell, Flushing, N.Y., assignors to The Wilcolator Company, Elizabeth, NJ., a corporation of Delaware Application August 19, 1957, Serial No. 679,018

8 v (Cl. 20G-166) This invention relates to electrical switching devices .or units, and, more particularly, to switching mechanism which is constructed 'and arranged to be operated by means of thermostats and other snap-action devices. The switchingunits are` used, among other things, for the'automatic control of heating or cooling apparatus such, for example, as electric ranges and refrigerators. 'In such apparatus, particularly in the smaller sizes, space is at a premium. It is, therefore, important to have all automatic control mechanism, such for example, as the electrical switching devices and the thermostats or other snap-action devices which operate them, constructed to the smallest' practicable dimensions consistent with adequate capacity and reliability. Thus, it is important that the power of a thermostat be sufficient to actuate, without fail, the switching mechanism with which it is associated, but heretofore there has been a tendency for switching mechanisms to require considerable -force forl their actuation in order to produce the proper pressure between their movable and stationary contacts. Consequently there hasalso been a tendency to make 'the thermostat of over-sizedvdimensions in order that it may have suilcient power to provide reliability in the voperation of the switch mechanism.

The primary object of our present invention is to provide an electrical switching unit of the double pole type 4which has sufficient current carrying and circuit breaking capacity to control the circuits of the apparatus mentioned and constructed to require the application of only a comparatively small force for its operation so that it can be successfully operatedbya snap-action device of small power and, consequently, inexpensive in cost of .manufacture and occupying asmall amount of space in the apparatus. v y Another object of our invention is to provide in a ',switching mechanism an arrangement of two stationary contact members andA an interconnecting movable con- `tact member such that, even with comparatively light `.contact pressures, the vresistance to current flow at the inter-engaging surfaces of such contact members .will be Iaminimum.' .a

Anotherobject of our invention is to provide a switch- 4ing mechanism,.which, although having comparatively.

flightcontact pressures, its movable contact member is operated in such a manner as to open the circuit of the apparatus mentioned without damage to the contacts even after long continued use.

In accordance with our invention, the switch mechanism comprises a pair of fixed contact members and a bridge member of lightweight and mass, and held in engagement with the fixed contacts by means of a spring. The actuator of the snap-action dev ice is arranged to strike the outer end of the bridge member which extends some distance beyond the outer lixed contact member,

` and since the bridging member is arranged to pivot on the inner fixed contact, a leverage is provided so that l only a small force is required to swing the bridge memr ber and open theswitch.

In order to provide a rocking pivot contact between the ICCy bridge member and the inner fixed contact member, a pair of aligned upward projections are formed in the upper surface of the bridge member near its inner end. These two projections are semi-circular in shape, so that a substantially frictionless rocking engagement is provAlso the outer fixed contact members are arranged to be vertically ,adjustable individually, and in this way the surfaces of these contacts can be levelled with ythe operating surface ofthe actuator so as to give precise 'simultaneous opening of the two pairs of switch contacts when the actuator snaps to the down or off position.

The switch mechanism of our invention will be more fully understood by referring to the following description and the accompanying drawings illustrating embodiments of the invention in double pole single throw and double pole double throw switchy mechanism.

In these drawings:

Fig. 1 is a plan view of the switching double pole single throw type;

Fig. 2 is a view in vertical section taken on line 2 2 of Fig. l, the arrows showing the direction;

Fig. 3 is a central vertical section taken on line 3--3 of Fig. 1;

Fig. 4 is a view of the unit in front elevation with the switch operating member shown in section as indicated by line 4--4 of Fig. 1;

Fig. 5 is a perspective view of the principal elements of the switch mechanism, and

Fig. 6 is a fragmentary view of a single' pole, double throw switch, being a view in vertical section somewhat similar to Fig. 2.

Referring to the drawings the mechanism of the switching unit is mounted within and upon a terminal block 1 of suitable insulating material, advantageously of a resinous compound such as Bakelite. Within this block suitable cavities and mounting surfaces are formed to receive and support the various parts of the switching mechanism.

In Figs. l to 5 there s illustrated a double pole, single unit of the throw switch mechanism, the right and left hand halves v*of which, as viewed in Figs. 1, 4 and 5, are substantially v identical. The lower terminal members are indicated at 2 and 2a, and the ,upper terminal membersat lSand 3 a.

l'The lower terminal members 2 are symmetrical to one another, that is, are madre in Yright and lefts, and are pro- A'vided with conventional terminal screws.4 and 4a to `'which conductors are securedfor the circuit which is to be controlled. The two upper terminal members 3 are identical and are provided with connection screws 5 and 5a. Lower terminal members 2 and 2a are secured in position on terminal block 1 by means of rivets 6 and 6a,

While the upper terminal members 3 and 3a are secured to the terminal block by rivets 7 and 7a.

,purposes rigid members.

lover at their upper ends in a conventional manner to secure the contact members lirmly in position.

In spaced relation `to these inner contact members 8 and 8a and also arranged approximately in the same horizontal plane there are two outer fixed contact members 9 and 9a. The working surfaces of these members also face downwardly and are rounded instead of being flat, and

`these contact members are mounted at the ,outer ends of Asupporting members 10 and 10a in the form of sheet metal springs to permit the contact members 9 and 9a to `be adjusted vertically. These contact members 9 and 9a are xed to the ends of spring members 10 in much the same way as the inner contact members y8 are mounted.

The inner ends of the supporting spring members 10 are perforated and firmly secured in position by the lower heads of the rivets 7 and 7a which support the upper terminal members 3 and 3a. To assure good electrical contact between members 10 and terminals 3 even in the event the rivet connections are not sufciently tight or become loose, spot welds 7w may be employed also to secure the inner ends of members 10 to terminals 3. At the outer vends of these terminal members there are two adjusting screws .11 and 11a which are threaded into 'apertures in terminal Ymembers 3 and 3a, and the inner lends of these screws .are arranged to engage the upper ends of the contacts 9 and 9a respectively to provide adjustment for these 'contacts and to hold them fixed `in adjusted position.

lThe movable contact members 12 and 12a of the switching mechanism are constructed in the form of light, rigid sheet metal strips which are arranged to somewhat more "than bridge the distance between the inner fixed contact members 8 and 8a and the vouter fixed contact members -9 and 9a. Advantageously they are of a highly conducthe bridge members to be engaged by an actuating member 13. It is important that the two bridge members be comparatively light in weight inasmuch as they are held inA closed position against the downwardly facing stationary contact members by means of the small helical springs 14 and 14a. The lower ends of these springs are received in recesses in terminal block 1, as shown in Fig. 2, and their upper ends fit over positioning formations or knobs 15 which are pressed downwardly from the lower surfaces of the bridge members 12 and 12a respectively at points substantially midway, or a little to the rearwardly of midway, between the respective pairs of fixed contacts 8, 8a and 9, 9a.

Adjacent .the inner end of each bridge Imember and opposite its .inner fixed contact a pair of projections y16 having outer surfaces of semi-cylindrical shape are formed. In forming each .of these kprojections two par- V[allel v.cuts are lmade and the material between these .cuts

is forced upwardly .out of .the plane of .the bridgemember vand into the semi-'cylindrical shape. These '.formationsare arranged in lateral alignment with one another and their semi-cylindrical surfaces bear against the flat surfaces of the corresponding inner fixed contact member 8 or 8a, as the case may be, making line contact therewith at all times.

In substantial alignment with thcse'two semi-cylindrical projections or formations and projecting from the opposite edges of each bridge member are two pivoting ears 17. They enter vertical slots 18 formed in the adjacent parallel walk of the cavities in terminal block 1 within which the vstationary contacts kand bridge members are located. The ears'17. fit loosely withinltheseslotsl.

lt will fbeunderstood that the actuating member 13 is the output member or snap arm of a snap-action device such, .for example, .as a thermostat and as shown in the drawings this member is in its up position which is determined by means of an adjusting screw 19 `arranged engages a nose 20 which projects fromv the end of the actuating member 13. It was mentioned previously that actuator 13 spans the distance between the two movable contact or bridging members 12 and 12a so as to operate them simultaneously. The bridging members are provided with slightly upturned tongues 21 and 21a which are engaged by the lower surface of'actuator 13 adjacent its side margins, as shown in Figs. `1 and 5.

Stop screw 19 is adjusted to allow actuating member 13 to rise sufliciently on its upward movement so as to leave a predetermined pre-travel space 22 between the tongues 21 and 21a and the lower surface of the actuating member. This pre-travel space permits actuating member 13 to accelerate before engaging the tongues 21 and 21a so as to open the bridging members 12 and 12a with a hammer blow action. Hence the bridging members separate very rapidly from stationary contacts 9 and 9a.

.This reduces damage to thecontacts by 'arcing to'a minimum. The downward Imovement of the bridging 'members 12 and 12a 'under the actuation'ofmember 13 Iof the snap-action'device isarrested -by means ofa stop kmember '23 formed on terminal block lvertically beneath bridging member 12.

The switching mechanism .is .calibrated 'by first placing the actuator 13 .in its down position, that is, bysetting the vsnap action device to .hold the switching mechanism in open position with .the two bridging members 12 and 12a in their lowermost positions with member `12 in contact with stop lug 23. One of the setscrews, for example, the left hand setscrew 11 is first adjusted yto lower its contact 9 until it just touches bridge member 12 and closes the circuit. Setscrew 11a is similarly adjusted. This levels the contacts 9 and 9a into parallelism with the surface of actuating member 13. Then yscrews 11 and 11a are each backed off a vpredetermined amount, for example, about .01 inch. This .establishes the travel of the bridge members between their closed and open positions. Next `the snap-action device is set to raise actuating member 13 to its upper position-the closed position of the switching mechanism. Stop screw 419 is `turned down until it engages the nose 20 of actuator 13. Then it is backed off to provide the desired amount of pre-travel, that is to say, approximately one-half of the total stroke of the actuator, so as to give the impact action at the switch opening.

The modified form of the switch mechanism as shown in Fig. 6 is a single pole switch with a double throw instead of a single throw. The switch construction is somewhat similar to one-half of that (left hand half as seen in Figs. 1, 4 and 5) described abovewith the exception that an additional outer lstationary contact 24 is mounted on the stop lug 23 which s placed directly beneath contact 9. The stop lug isshortened somewhat and provided with a'central opening 'through which the stem 2S of the contact v24 is received. It will be understood that a suitable vconnection is provided from the contact 24 to a connection screw (not shown) on the exterior 'of the terminal block.

The adjustment and operation of the single Polt-double throw form of the switching mechanism (Fig. 6) is similar to that previously described, the difference being that'when the movable contact or bridging member 12 is moved downwardly by the actuator 13, the circuit is broken between the inner stationary vcontact 8 and the outer stationary contact 9, anda circuit is established between inner contact 8, and the lower additional contact 24.

A double pole, double 'throw switch according to this invention may Icomprise a .switch as shown in Figs. 1 through 5 modified to provide lower stationary contacts in the manner taught by the disclosure of Fig. 6, provision further being made however for Yswiveling or the like of actuating member 13'to assure proper contacting of the lower contacts.

By means of our improved .switch mechanism the power required for operation .of suchdevices has been .5 greatly reduced so that a snap-action device such as heretofore used to operate a single pole, single or double throw switch is adequate to operate our double pole, single or double throw switch. Thus, for example, referring to Fig. 2 coil spring 14 may exert a force of approximately 20 grams upwardly against the movable sw1tch or bridging member 12 and since this force may, for example, be applied midway between the inner and outer stationary contacts 8 and 9 a force of 10 grams will be exerted by the bridging member against each of these contacts. The same holds true for bridging member 12a and its associated parts. The tips of tongues 21 and 21a of the respective bridging contact members extends suliiciently to the left of stationary contacts 9 and 9a before being engaged by the actuating member 13 to provide a leverage ratio such that only about 7 grams downward force by the member 13 on each of the bridging member tongues, in this particular example, is required for actuation.

We have devised a double pole switch mechanism which not only requires the application of an extremely small force for its operation, but also has a small amount of motion of the movable switch members between the open and closed circuit positions. At the same time adequate pressure is applied between the contact surfaces so that the switching mechanism has ample current-carrying and circuit-breaking capacities for the circuit of the apparatus with which the device is used.

Where the terms upwardly and downwardly have been used herein or are used in the appended claims, they are to be understood to be relative directional indications only, and in space to have no meaning other than that upward is opposite from downward, and vice versa.

It will be understood that the scope of our invention is set forth in the appended claims.

We claim:

1. An electric switch mechanism comprising trst and second fixed contact members, means for supporting said members in spaced relation in approximately the same plane, a movable, substantially rigid contact member bridging the space between said members, a spring acting in a substantially normal direction on said movable contact member intermediate said fixed contact members and urging the movable member into engagement with both of said members, means for pivoting said movable contact member adjacent said irst fixed contact member, and switch operating means engageable with said movable contact member adjacent said second fixed contact member for moving the movable contact member out of engagement with said second contact member to open the switch, said spring maintaining the movable contact member in engagement with said first fixed contact member during such movement.

2. An electric switch mechanism as set forth in claim 1, wherein the movable contact member is of metallic sheet material and the surface of the first fixed contact member is substantially fiat, the said movable contact member having a pair of projections in lateral alignment with one another whose outward surfaces are semi-cylindrical and engage the substantially fiat surface of said xed contact member to provide a rocking contact therewith as the switch is opened and closed.

3. An electric switch mechanism as set forth in claim 2 wherein the switch parts are supported by means of a terminal block having a cavity therein with substantially parallel vertical walls, the said first and second fixed contact members and the movable contact member being disposed in said cavity, and said movable contact member having a pair of pivoting ears projecting laterally from the edges of said member opposite the pair of semi-cylindrical projections thereon, the opposite walls of said cavity having each a vertical groove and the said pivoting ears being received within said respective grooves.

4. An electric switch mechanism as set forth in claim l,

wherein the switch operating means is a snap-action device, the switch actuating member of which is spaced from the movable contact member of the switch when the switch is in closed position thereby causing the actuating member, when opening the switch, to produce a hammer blow action on the movable contact member resulting in rapid opening of the switch contacts.

5. An electric switch mechanism comprising first and second fixed contact members, means for supporting said members in spaced relation with the working surfaces thereof facing downwardly and in approximately the same plane, a movable, substantially rigid contact member of light weight and small mass bridging the space between said members, a spring acting in a substantially normal direction on said bridging contact member and arranged to support said member in engagement with the downwardly facing surfaces of said fixed members, means for pivoting said movable contact member adjacent said first fixed contact member, and switch operating means engageable with said movable contact member adjacent said second fixed contact member for moving the movable contact member downwardly out of engagement with said second contact member to open the switch, said spring maintaining the movable contact member in engagement with said first fixed contact member during such movement and operating to raise the opposite end of said member into engagement with said second fixed contact member to reclose the switch on the upward movement of such operating member.

6. An electric switch mechanism as set forth in claim 5, wherein the switch operating means is a snap-action device, the switch actuating member of which is spaced from the movable contact member of the switch when the switch is in closed position thereby causing the actuating member, whenopening the switch, to produce a hammer blow action on the movable contact member resulting in rapid opening of the switch contacts.

7. An electric switch mechanism comprising two bladelike movable contact bridging members disposed side-byside and parallel to one another, inner and outer fixed contacts supported by said terminal block above each of said bridging members and having their contact surfaces facing downwardly, means for pivoting each of said bridging members adjacent said respective inner fixed contacts, a compression spring disposed beneath each of said blade-like members and engaging therewith between said fixed contacts, said springs supporting their respective bridging members in engagement with said contacts when the switch mechanism is in closed position, and a common actuator arranged to engage the outer ends of said bridging members, said actuator contacting said bridge members at a distance beyond said fixed outer contacts which is substantially one-half of the bridging space between said contacts, and means for vertically adjusting said outer fixed contacts so as to level said contacts with the surface of said actuator in order to produce precise simultaneous opening of the switch mechanism when said actuator is depressed.

8. An electric switch mechanism as set forth in claim 7, wherein the common actuator is the operating member of a snap-action device and said actuator is spaced from said bridging members when the switch mechanism is in closed position thereby causing the actuator, when opening the switch mechanism, to produce a hammer blow action on said bridging members resulting in rapid opening of the switch contacts.

References Cited in the tile of this patent UNITED STATES PATENTS 2,059,702 Matthias Nov. 3, 1936 2,490,280 Rees Dec. 6, 1949 2,647,968 Byam Aug. 4, 1953 2,698,369 Daily et al Dec. 28, 1954 2,700,079 Haydon Ian. 18, 1955 

